Conventionally, plural plate-shaped synthetic corundum pieces are prepared and these synthetic corundum pieces are bonded to manufacture a flow cell made by synthetic corundum.
Herein, when bond these by using an adhesive material, a boundary surface comes into existence in the bonding surface, then light refraction or light reflection occur, also, when make these thermal fusion, air bubbles confined in the bonding surface.
Therein, the applicant of this application suggested patent document 1-3.
The bonding method disclosed in the above patent document 1-3 is basically same, that is, at first cut off synthetic corundum pieces from a crystal block, polish the surface of each synthesis corundum piece, and overlap each polished surface, strongly press (pinch) the one end side of the two faced pieces of the synthetic corundum.
The press strength is assumed as interference fringe is inspected between surfaces of the synthetic corundum pieces, in this state, heat the two pieces of synthetic corundum at melting point (2,030 degrees Celsius) or less, then, it gradually assumes a fusion bonding state from one end of the synthetic corundum piece to the other end.
In the above, it becomes an optical contacting state or a chemical pressurized fusion bonding state in the strongly pressed one end side, the interference fringe disappears by heating, it is considered that the optical contacting state or the chemical pressurized fusion bonding state continues to the other end side by heating.
And, an optical boundary surface does not exist in the synthetic corundum body bonded together in this manner, then an extremely superior three-dimensional structure is provided.